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Gas Exchange Mechanisms in Insects
May 22, 2025
Lecture Notes: Gas Exchange in Terrestrial Insects
Overview
Focus on gas exchange in terrestrial insects
Anatomy, adaptations, and water loss prevention
Anatomy of Terrestrial Insects
Exoskeleton
Made of chitin: hard, fibrous material for protection
Contains a lipid layer to prevent water loss
Ventilation and Gas Exchange
No lungs
Tracheal system instead
Adaptations to Limit Water Loss
Essential for survival on land (terrestrial environment)
Key Adaptations:
Small Surface Area to Volume Ratio
Limited water evaporation surface
Lipid Layer
Makes the exoskeleton waterproof
Spiracles
Tiny holes on the abdomen for gas exchange
Can open and close to control water loss
Tracheal System
Components: Spiracles, Tracheae, Tracheoles
Spiracles
Valve-like openings along the abdomen
Control water loss and gas entry/exit
Tracheae
Network of internal tubes
Rings to strengthen and prevent collapse
Tracheoles
Smaller tubules branching from tracheae
Deliver oxygen to respiring cells
Gas Movement in the Tracheal System
Simple Diffusion
Oxygen used up, carbon dioxide produced by respiring cells
Concentration gradient allows diffusion
Mass Transport
Muscle contractions in the abdomen move gases
Increases volume of gases exchanged
Fluid Pressure Changes
Occurs during flight
Switch to anaerobic respiration producing lactate
Lowers water potential, causing water movement
Decreases pressure and volume in tracheoles, drawing in air
Summary
Large Surface Area
: Numerous fine tracheoles and spiracles
Short Diffusion Pathway
: Thin tracheole walls, short distance between spiracles and tracheal system
Maintaining Concentration Gradient
: Respiring cells use oxygen, produce carbon dioxide
Importance of maintaining a steep diffusion gradient for efficient gas exchange
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